The present invention relates to a lens array substrate and a liquid crystal display. Particularly, the invention relates to the liquid crystal display and the lens array substrate used for the above display which is used in a projector.
A transmissive liquid crystal display mainly comprises a liquid crystal panel and a power source device (back light). FIG. 1 is an exploded perspective view that schematically shows the inner structure of a liquid crystal display panel 1. The transmissive liquid crystal display panel 1 comprises a back substrate 2, a front substrate 3, and a liquid crystal layer 4 which is sealed therebetween. The back substrate 2 comprises pixel electrodes 6 and TFTs (thin film transistor) 7 formed for each pixel region on the surface of a glass substrate 5, and an orientation film 8 is formed on the pixel electrodes and TFTs. In the front substrate 3, color filters 10 for red (R), green (G) and blue (B) are formed on the back surface of a glass substrate 9, a transparent electrode (ITO) 11 is formed to cover the back surfaces of all the color filters, and an orientation film 12 is formed on the transparent electrode 11. The liquid crystal layer 4 is filled in a space formed between the orientation film 12 on the front substrate 3 and the orientation film 8 on the back substrate 2, and the periphery of the liquid crystal layer 4 is sealed with a sealing spacer (not shown). The back surface of the back substrate 2 and the front surface of the front substrate 3 have polarizing plates 13 and 14, respectively on the opposite sides.
Light is emitted by a light source device from the back of the liquid crystal display panel 1, and ON/OFF state of the voltage applied to each pixel electrode 6 and the transparent electrode 11 is controlled by the TFTs 7, to control the transmission and the blocking of the light in each pixel on the liquid crystal display panel 1, in order to generate an image.
In the liquid crystal display panel 1, the gaps between the color filters 10 are covered with black matrixes 15 to prevent the light from the light source from passing through the gaps, in order to improve the contrast in an image for a sharp image. The black matrixes 15 are made from a light-absorbing resin or a chromium film. The matrixes 15 are formed by printing, deposition or sputtering, then patterns are formed thereon by the photolithography.
On the other hand, the liquid crystal display is used in commercially available presentation tools such as a liquid crystal projector, as well as used as a display section of a personal computer (PC), a personal digital assistant (PDA), and a mobile phone. Particularly, the liquid crystal projector is commonly used as a projector for presentation in a meeting, or as a digital cinema.
FIG. 2 illustrates the construction of a color liquid crystal projector 21. A light source device 22 such as a halogen lamp having a reflector is provided with a dichroic mirror 23 in front of the device 22 at an angle of 45xc2x0, which transmits only blue light 34B while reflects red light 34R and green light 34G. In the direction to which the light passed through the dichroic mirror 23 proceeds, a total reflection mirror 24 is provided at an angle of 45xc2x0, and in the direction to which the light reflected by the total reflection mirror 24 proceeds, a liquid crystal display panel 25 for single color for generating a blue image is provided, which, in turn faces the side surface of a prism 26 having reflective surfaces in two directions. In the direction to which the light reflected by the dichroic mirror 23 proceeds, a dichroic mirror 27 which reflects green light 34G while transmits red light 34R is provided at an angle of 45xc2x0, and in the direction to which the light reflected by the dichroic mirror 27 proceeds, a liquid crystal display panel 28 for single color for generating a green image is provided, which, in turn faces the back surface of the prism 26. In the direction to which the light passed through the dichroic mirror 27 proceeds, a total reflection mirror 29 is provided at an angle of 45xc2x0, and in the direction to which the light reflected by the total reflection mirror 29 proceeds, a total reflection mirror 30 is provided at an angle of xe2x88x9245xc2x0, and in the direction to which the light reflected by the total reflection mirror 30 proceeds, a liquid crystal display panel 31 for single color for generating a red image is provided, which, in turn faces another side surface of the prism 26. A projection lens 32 is provided on the front surface of the prism 26.
In the white light emitted from the light source device 22, blue light 34B passes through the dichroic mirror 23, reflected by the total reflection mirror 24, then incident on the liquid crystal display panel 25. When the blue light irradiates on the liquid crystal display panel 25, the light passed through the liquid crystal display panel 25 generates a blue image, which, in turn, is reflected to the forward direction by the reflection surface of the prism 26. In the white light emitted from the light source device 22, green light 34G is reflected by the dichroic mirror 23, reflected by the dichroic mirror 27, then incident on the liquid crystal display panel 28. When the green light 34G irradiates on the liquid crystal display panel 28, the light passed through the liquid crystal display panel 28 generates a green image, which, in turn, passes through the prism 26. In the white light emitted from the light source device 22, red light 34R is reflected by the dichroic mirror 23, passes through the dichroic mirror 27, reflected by the total reflected mirrors 29 and 30, then incident on the liquid crystal display panel 31. When the red light 34R irradiates on the liquid crystal display panel 31, the light passed through the liquid crystal display panel 31 generates a red image, which, in turn, is reflected to the forward direction by the reflection surface of the prism 26.
Thus, the blue image generated on the liquid crystal display panel 25, the green image generated on the liquid crystal display panel 28, and the red image generated on the liquid crystal display panel 31 are superimposed by the prism 26 to make a color image, which, in turn is projected on the projection lens 32. The color image passed through the projection lens 32 is focused on the front screen 33. The front screen 33 thus display the color image.
In this technical field, there is a need for a smaller projector having higher luminance in order to improve the usability and the quality of an image. Also, there is a need for a liquid crystal projector and a personal computer to have higher resolution. In response, the number of the pixels on the liquid crystal display panel is expanding. However, even if a pixel is reduced in size in order to increase its number, it is difficult to reduce the size of the TFT and its wiring in each pixel. The ratio of the pixel open area (open area ratio) gets lower as the area of a pixel is reduced for increased number of the pixels. Therefore, in order to keep the luminance of the screen even when the open area ratio is reduced, it is necessary to increase the amount of the light from the light source device.
Thus, the light source device of a liquid crystal display apparatus for a liquid crystal projector and an image display emits more and more amount of the light. However, when the light emitted from light source device increases, the light irradiating on the TFTs and their wirings increases accordingly, so that carriers are prone to be excited by the light, which may lead to unstable operation or malfunction of the TFT.
In order to improve the efficiency of the light while suppressing the increase in the light supplied from the light source device, a lens array is provided on the back substrate. FIG. 3 is a cross-sectional view that schematically shows the liquid crystal display panel 41 provided with a lens array 47 on a back substrate 42. In the back substrate 42 of the liquid crystal display panel 41, lens-shaped patterns are formed on the surface of a lens resin layer 45 formed on the glass substrate 44, then a sealing resin layer 46 is applied on the lens resin layer 45 to make a planer surface. The lens resin layer 45 and the sealing resin layer 46 have different refractive indexes, thus forming a lens array 47 at the interface of the lens resin layer 45 and the sealing resin layer 46. Furthermore, a cover substrate 64 made from glass is adhered to the sealing resin layer 46, a transparent electrode (ITO) 48 is formed to cover the all surface of the cover substrate 64, and an orientation film 49 is provided on the surface of the transparent electrode 48. On the back substrate 42, a surface substrate 43 is adhered via a liquid crystal layer 51 the peripheral of which are sealed by a spacer 50. In the front substrate 43, color filters 53 and black matrixes 54 are formed on the back surface of a glass substrate 52, pixel electrodes 55 and TFTs 56 are formed on the color filters 53 and the black matrixes 54, and an orientation film 57 is formed on the pixel electrodes 55 and TFTs 56. On the surface of the front substrate 43 and the back surface of the back substrate 42, polarizing plates 58 and 59 are disposed.
In the liquid crystal display panel 41, the light emitted from the light source device and incident on the back substrate 42, when passing through the lens array 47 as shown in FIG. 4, is collected to each pixel opening 60 (pixel electrode 55 and color filter 53) by the lens array 47, to pass through the opening 60. As a result, the light emitted from the light source is not blocked by the black matrixes 54, instead, almost 100% of the light passes through the pixel opening 60 to exit in forward direction, which significantly improves the efficiency of the light. Also, as the light passed through the lens array 47 is collected to the pixel opening 60, the light is less likely to enter the TFTs 56 or their wirings, which prevents unstable operation or malfunction of the TFTs 56.
However, the lens array is difficult to be formed in an ideal shape. The boundary edge between lenses constituting the lens array may be rounded, so that, the light passed through the lens array irradiates on the TFTs and the TFT wirings in practice. It is difficult to satisfactorily prevent unstable operation or malfunction of the TFTs.
In order to solve the above problem, an improved liquid crystal display panel 61 has a cover substrate 62 made from glass on the sealing resin layer 46 of the back substrate 42, as shown in FIG. 5. Furthermore, light blocking members 63 (these may be sometimes referred to as black matrixes) are provided between the cover substrate 62 and above transparent electrode 48 at the positions corresponding to the boundary edges of the lens array 47, to prevent light from irradiating on the TFTs 56.
The liquid crystal display panel illustrated in FIG. 5 has features to minimize the amount of light irradiating on the TFTs to prevent unstable operation or malfunction of the TFTs. The blocking member used to block incident light on the TFTs is made from a Cr (chrome) single layer film (the reflectance is around 60%) having low reflectance.
A light blocking member made from a material having low reflectance has high light absorptance at the same time. In a liquid crystal display panel having a structure as shown in FIG. 5, the blocking member raises its temperature by the light emitted from the light source device, which causes the rise in the temperature of the liquid crystal display panel as a whole. This rise in the temperature affects the liquid crystal and the orientation film, and the quality and the life of the liquid crystal display panel itself. When the temperature of the liquid crystal display panel reaches 60 to 70 degrees centigrade, the liquid crystal may decompose or the characteristics of the orientation film may change, which leads to the change in the orientation of the liquid crystal, then deterioration of the liquid crystal display panel. Particularly in recent years, as the pixel in the liquid crystal display panel gets finer as described, the black matrixes and the blocking members occupy wider area than ever, and more amount of light is emitted to improve the luminance of the liquid crystal display panel. The rise in temperature of the liquid crystal display panel imposes a big problem.
The purpose of the present invention is to solve the above problem. The present invention provides a lens array substrate and a liquid crystal display apparatus which can prevent unstable operation and malfunction of the elements such as TFT, by suppressing the rise in the temperature of the liquid crystal display panel.
The invention provides a lens array substrate having a lens array made from a plurality of lenses, wherein light blocking members are provided along the regions corresponding to the boundaries between the lenses, and the surface of the light blocking member on which the light is incident has high reflectance against light. Typically, the high reflectance surface has reflectance of 70% or more, more preferably, 80 to 90% or more reflectance against light. The surface of the light blocking members opposite to this high reflectance surface may have either high reflectance, high light absorptance, high diffusivity, or any other characteristics.
The lens array substrate according to the invention can collect the incident light by each lens in the lens array. Also, as the blocking members are provided along the regions corresponding to the boundaries between the lenses, they can effectively block the light passed through these boundaries. The lens boundaries may have molding error or rounded edge, so that the light can pass through these edges. But according to the invention, the light thus passed is prevented from diffusing to irregular direction. In addition, the light incident surface of the light blocking member has such high reflectance so that it is not prone to absorb the blocked light nor to raise its temperature, which minimizes the rise in temperature of the lens array substrate.
According to an embodiment of the invention, the light blocking member is formed with Al or Ag, which makes a high reflectance surface. It facilitates the handling of the light blocking member, also reduces the cost. Especially, when Ag is used, the reflectance as high as about 98% can be obtained.
According to another embodiment of the invention, at least one component which is contained in the member adjacent to the light blocking member is added therein. Thus, the component contained in the adjacent member cannot diffuse to the light blocking member, which prevents the change in the quality of light blocking member and improves the reliability of lens array substrate. For example, when the blocking member is adjacent to the glass surface, Si may be added to the light blocking member. When the adjacent member comprises mainly of Al, Alxe2x80x94Sixe2x80x94Cu or Alxe2x80x94Si may be used for the light blocking member.
According to another embodiment of the invention, a layer to improve the adhesion of the light blocking member supporting member and the light blocking member itself, is interposed therebetween. This construction prevents the light blocking member from separating from its supporting member, to improve the reliability of the lens array substrate.
According to another embodiment of the invention, the light exiting surface of the light blocking member has high light absorptance, i.e., the light incident surface of the light blocking member has high reflectance while the light exiting surface of it has high light absorptance. Thus, when the light passed through the lens array substrate is reflected, the light blocking member can effectively absorb the returned light. That is, the light blocking member can prevent the light from being re-reflected by the light blocking member and becoming stray light.
In order to obtain high light absorptance in the light exiting surface of the light blocking member, the surface may be formed with Cr, an oxide (for example, chrome oxides) or polymers. The surface formed with a chrome oxides has higher light absorptance compared to the surface formed with Cr. Otherwise, a chrome oxide can be formed on the Cr surface. When the surface is made from a polymer, the surface with high light absorptance can be formed in ambient atmosphere at room temperature. When a photosensitive polymer such as photosensitive polyimide is used as a polymer, a surface with high light absorptance can be formed by the photolithography.
According to another embodiment of the invention, a light blocking member has an etching stop layer between a layer constituting the high reflectance surface and a layer constituting the high light absorptance surface. In this embodiment, when etching for patterning the upper layer of the layer constituting the high reflectance surface and the layer constituting the high light absorptance surface, the etching stop layer prevents the lower layer from being etched. Thus, the lower layer can be prevented from being over-etched and having too narrow pattern width by side-etching.
According to another embodiment of the invention, the layer constituting the high light absorptance surface may be formed on the glass surface oriented to the incident light, and the layer constituting the high reflectance surface is formed on the high light absorptance surface. That is, when the light blocking member having the high reflectance surface and the high light absorptance surface is formed on the glass surface oriented to the incident light, the layer constituting the high light absorptance surface is adhered to the glass surface. For example, a Cr layer constituting the high light absorptance surface adheres to the glass more securely than an Al layer constituting the high reflectance surface. Therefore, the light blocking member formed on the glass surface oriented to the incident light can adhere to the glass surface more securely with a simple construction.
In the liquid crystal display apparatus according to the invention, the lens array substrate and the opposite substrate recited in one of the claims 1 to 12 are disposed in opposite side via a liquid crystal layer, pixel electrodes are formed in one of the lens array substrate or the opposite substrate, in opposite positions of each lens in the lens array, and a transparent electrode is formed on the other of the lens array substrate or the opposite substrate.
The liquid crystal display apparatus according to the invention collects the incident light to the pixel electrodes by each lens in the lens array, which improves the efficiency of the light. Also, as the light blocking members are provided along the regions corresponding to the boundaries of the lenses, the light passed through these boundaries can be effectively blocked by the light blocking members, which prevents the light passed through the molding error or rounded edge of the lens boundary from entering in the element such as TFTs. Any unstable operation of the elements caused by the light thus entered can be effectively prevented. Furthermore, the light incident surface of the light blocking member has such high reflectance that it is not prone to absorb the blocked light nor raise its temperature, which minimizes the rise in the temperature of the liquid crystal display apparatus.
The components as described above can be combined in any way as desired.